Database initialization if empty db detected.

When setting up the quick docker Kea environment, I encountered a problem with an inconvenient step of manually preparing the database to work with Kea. The docker environment discourages manual involvement in running containers.

Most other systems I used set up a database automatically when an empty system is detected. Examples: Nextcloud, Wordpress, nginx, tomcat, mosquito, homeassistant and many more.

This feature would be handy, but not required.